Creating and Using Jest Mocks
test.js
When you need to test how your code interacts with functions, you can use Jest's jest.fn() to create a mock function. A mock function lets you track how it is used, such as how many times it was called, what arguments it received, and what it returned. This is especially helpful when you want to isolate the function being tested from its dependencies.
You can use Jest's mock assertion methods to make checks about the mock function's behavior. For example, .toBeCalledTimes(number) checks how many times the mock function was called. Other useful matchers include .toHaveBeenCalledWith(arg1, arg2, ...) to check what arguments were passed, or .toHaveReturnedWith(value) to check what values were returned.
By using mock functions, you can make your tests more focused and reliable, ensuring that your code interacts with its dependencies as expected.
1. What does jest.fn() do in Jest?
2. How can you check how many times a mock function was called in Jest?
Merci pour vos commentaires !
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test.js
When you need to test how your code interacts with functions, you can use Jest's jest.fn() to create a mock function. A mock function lets you track how it is used, such as how many times it was called, what arguments it received, and what it returned. This is especially helpful when you want to isolate the function being tested from its dependencies.
You can use Jest's mock assertion methods to make checks about the mock function's behavior. For example, .toBeCalledTimes(number) checks how many times the mock function was called. Other useful matchers include .toHaveBeenCalledWith(arg1, arg2, ...) to check what arguments were passed, or .toHaveReturnedWith(value) to check what values were returned.
By using mock functions, you can make your tests more focused and reliable, ensuring that your code interacts with its dependencies as expected.
1. What does jest.fn() do in Jest?
2. How can you check how many times a mock function was called in Jest?
Merci pour vos commentaires !
